VATICAN CITY -- Pope Benedict XVI broke his recent silence on the clergy-abuse scandal Thursday, complaining that the church was under attack but saying that "we Christians" must repent for sins and recognize mistakes.

The main U.S. victims group quickly dismissed his comments, saying they are meaningless unless the pontiff takes concrete steps to safeguard children from pedophile priests.

Benedict made the remarks during a homily at a Vatican Mass for members of the Pontifical Biblical Commission.

"I must say, we Christians, even in recent times, have often avoided the word 'repent,' which seemed too tough. But now under attack from the world, which has been telling us about our sins ... we realize that it's necessary to repent, in other words, recognize what is wrong in our lives," he said.

"Open ourselves to forgiveness ... and let ourselves be transformed. The pain of repentance, which is a purification and transformation, is a grace because it is renewal and the work of divine mercy," he said.

Victims of clerical abuse long have demanded that Benedict take more personal responsibility for the abuse, charging that the Vatican orchestrated a culture of cover-up and secrecy that allowed priests to rape and molest children for decades.

Those demands have intensified in recent weeks as the Vatican and the pope himself have been accused of negligence in handling some cases in Europe and the United States.

"Factual disclosures are not 'attacks' and 'penance' protects no one," said Mark Serrano, a spokesman for the Survivors Network of those Abused by Priests, the U.S. group.

"When the pope can't bring himself to utter the words 'pedophile priest' or 'child sex crimes' or 'cover-ups' or 'complicit bishops,' it's hard to have faith that he is able to honestly and effectively deal with this growing crisis," Serrano said in a statement.

Benedict's comments were his fullest allusion yet to the scandal since he sent a letter to the Irish faithful March 20 concerning what Irish-government inquiries have concluded was decades of abuse and church-mandated cover-up in the country.

In his letter Benedict chastised Irish bishops for failures in leadership and judgment, but took no responsibility himself or for the Vatican.